Defrost timer arrangement for making clear ice

ABSTRACT

A clear cube ice maker has a control circuit incorporating the defrost timer of a freezer and a bistable relay switch in the harvest mechanism. The relay switch, in response to a signal from the defrost timer, conditions the ice maker for a deferred harvest when the weigh switch is open (ice bucket full or ice bucket not in place) at the time of the signal or during the harvest. The relay switch is also in a circuit with an extra tray bottom heater to prevent the water from freezing to the bottom of the tray while awaiting the deferred harvest and is closed by the defrost timer and opened by a cam in the harvest mechanism.

United States Patent [191 Bright 1 DEFROST TIMER ARRANGEMENT FOR MAKINGCLEAR lCE [75] Inventor: James A. Bright, Dayton, Ohio [73] Assignee:General Motors Corporation,

Detroit, Mich.

[22] Filed: Nov. 29, 1973 [21] Appl. No.: 419,942

[ Feb. 11, 1975 3,75l,939 8/1973 Bright ..62/l37 3,775,992 l2/l973Bright ..62/35lX Primary Examiner-William F. ODea AssistantExaminer-Peter D. Ferguson Attorney, Agent, or Firm-Frederick M. Ritchie[57] ABSTRACT A clear cube ice maker has a control circuit incorporatingthe defrost timer of a freezer and a bistable TRAY SIDE AND [52] US. Cl62/137, 62/155, 622/2334: relay switch in the harvest mechanism Therelay 1 6 B4 switch, in response to a signal from the defrost timer, Cl.o d t on the ce a e o a efe red ar est hen [581 mid of Search ll 15 3the weigh switch is open (ice bucket full or ice bucket not in place) atthe time of the signal or during the [56] Reierences cued harvest. Therelay switch is also in a circuit with an UNITED STATES PATENTS extratray bottom heater to prevent the water from 3,643,458 2/1972Linstromberg et a1. 62/155 freezing to the bottom of the tray whileawaiting the 3,648,478 3/1972 Linstromberg 62/233 X deferred harvest andis closed by the defrost timer and NlChOlS et al... pened a cam in theharvest mechanism 3,675,437 7/1972 Linstromberg 62/137 3,714,794 2/1973Linstromberg et al. 62/137 5 Claims, 16 Drawing Figures IIOV Z 0 B235 72l 1:: I WEIGH i a I SWITCH A 3 y f 1 )L I L ""Z if z 2Z2 {TIMER I TRAYBOTTOM {SWITCH I HEATER [I l W i l LIMITER SWITCH PATENTED W 1 5 sum 3OF 6 IIIII 3.864.933 SHEET u 0F 5 PATENTED 5 PATENIEU FEB] 1 ms Sum 8 BF6 x ll/I/D o 4.. .a Q I a L e I I YHEATER 63 M60 DEFROST HEATER R OLTRAY SIDE AND BOTTOM HEATER DEFROST DEFROST TIMER CYCLE CHART I 480 MIN.

330 MIN.

CON TACTS DEFROST TIMER ARRANGEMENT FOR MAKING CLEAR ICE This inventionrelates to apparatus for making clear ice of the type taught in mycopending application Ser. No. 272,4l0, filed July I7, 1972 now U.S.Pat. No. 3,775,992 issued Dec. 4, I973 and, more particularly, to atiming arrangement for controlling such apparatus through the defrosttimer in a domestic refrigerator.

Clear ice has been a desire of users and a goal of manufacturers foryears. Apparatus for making clear ice, however, has been cumbersome andsuited only to commercial manufacture of ice. Heretofore, no one hassimplified clear ice makers to the point where they are suitable insize, cost and operation to the relatively small confines of the freezerin a domestic refrigerator.

Accordingly, an object of this invention is the provision of a methodand apparatus for making clear ice in a container in the freezer of adomestic refrigerator by containing water in a tray, heating the bottomof the tray to keep the lower portion of the water in a liquid state,freezing the top portion of the water starting at the interface betweenthe water and freezer air and continuing to freeze water downwardlytoward the bottom of the tray, periodically removing the frozen clearice portion before it extends sufficiently toward the bottom of the trayto entrap gas and minerals in the water, and timing the periodic removalthrough a defrost timer for said freezer.

A further object of this invention is a timing arrangement for a clearice maker in a freezer having an automatic defrost cycle and comprisinga tray containing a body of water, a grid in said tray displacing saidbody of water into cavities in said grid, fan means distributingsub-freezing air over the top surface of said body of water in said gridwhereby to initiate the freezing of clear ice along the interfacebetween said air and said top surface, and a bucket for storing saidclear ice, heating means to maintain said body of water in a liquidstate adjacent said tray below said clear ice, harvesting mecchanism forremoving said grid from said tray and depositing said clear ice in saidbucket, and a defrost timer for periodically defrosting said freezer,said heating means comprising a first heater for the sidewall of thetray and a second heater for the bottom wall of the tray, and controlmeans providing for continuous energization of said first heater andenergization of said second heater only when said bucket is full ofclear ice or not in said freezer, said defrost timer having bistablemeans for initiating the operation of said harvesting mechanism.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

IN THE DRAWINGS FIG. 1 is a fragmentary section through the freezercompartment of a domestic refrigerator showing in side elevation anautomatic clear ice maker;

FIG. 2 is a front elevational view taken along line 2-2 in FIG. 1 withparts broken away to provide a schematic representation of the clear iceharvesting cycle;

FIG. 3 is a sectional view taken along line 3--3 in FIG. 2;

FIG. 4 is a fragmentary sectional view taken along line 4-4 in FIG. 3and showing a portion of the water fill system;

FIG. 5 is a sectional view taken along line 5-5 in FIG. 3 and showing aninsulated and heated water containing tray;

FIG. 6 is a fragmentary sectional view taken along line 66 in FIG. 4;

FIG. 7 is a perspective view of a side by side refrigerator freezershowing the clear ice maker installed in a portion of the freezercompartment;

FIG. 8 is a perspective view of the clear ice maker of this invention inan ice harvesting mode;

FIG. 9 is a sectional view with parts broken away taken along line 9-9in FIG. 3 to show the ice harvesting mechanism and weight sensing means;

FIG. 10 is a side elevational view with parts broken away taken alongline 10-l0 in FIG. 9;

FIG. 11 is a sectional view of the ice harvesting mechanism taken alongline ll-ll in FIG. 10 to show an ice making cycle timer and drivemechanism;

FIG. 12 is a perspective view from the front side with parts broken awayto show ice harvesting mechanism for moving the ice grid and weightsensing means for sensing, first, the presence of an empty ice storagebucket and, secondly, a predetermined load of ice in the bucket;

FIG. 13 is a perspective view of the ice harvesting mechanism from theback side to show an ice making cycle timer and drive mechanism;

FIG. 14 is a sectional view of a water fill system suitable for'use withthis invention;

FIG. 15 is a schematic wiring diagram of a circuit arrangement includinga defrost timer for controlling the ice making cycle in the improvedmanner of this invention; and

FIG. 16 is a timer cycle chart interpreting the operation of the defrosttimer in FIG. 15.

GENERAL In accordance with the teachings of the aforementioned copendingapplication and with particular reference to FIG. 7, a domesticrefrigerator 20 is shown. The refrigerator is of the side by side typewherein a right side portion encloses a refrigerated food compartment 22and the left side portion encloses a lower freezer portion 24 forstoring frozen foods and an upper freezer portion 26 enclosing the clearice maker of this invention shown generally at 28. A vertical fulllength door 30 may be used to close both the upper and lower freezercompartments 24, 26.

In general, the clear ice maker 28 (FIGS. 1 and 8) includes a tray andheater assembly 34, an ice cube grid 36, an ice storage bucket assembly38, a weight sensing means 39 for bucket and ice, an ice harvestingmechanism 40, and a water fill system 42.

TRAY AND HEATER ASSEMBLY The tray and heater assembly 34 (FIGS. 4 and 5)is supported by bracket means 46 from a sidewall 48 of the freezercompartment 26. The assembly includes a drawn sheet metal housing 50forming on one side thereof a water containing tray 52 having a sidewall54 and a bottom wall 56 and on the other side thereof a cavity filledwith freon-filled urethane foam insulation 58. A pair of-heaters 60, 62surround the tray 52. Heater 60 is adapted for heating all foursidewalls 54 of the tray and thereby normally exposes the bottom side ofthe tray (beneath the ice) to above-freezing temperature. This retainsthat portion of water along the bottom side of the tray in a liquidstate. For this purpose, heater 60 is comprised of 90.8 inches of vinylcovered resistance wire rated at US volts, 6.5 7.5 watts, 250 ohms perfoot reference.

Heater 62 is adapted for supplying additional heat to the tray bottomwall 56 under certain circumstances to keep ice from freezing all theway down to the bottom wall, and is comprised of 41.7 inches of vinylcovered resistance wire rated at 1 volts, 2.8 3.2 watts, l,268 ohms perfoot reference.

Heater 60 is sandwiched between a sheet 66 of 0.005 aluminum foil and asheet 68 of 0.002 aluminum foil. Similarly, bottom wall heater 62 issandwiched between a sheet 70 of 0.005 aluminum foil and a sheet 72 of0.002 aluminum foil. The mating edges of foil sheets 66 and 68 areheat-sealed as are the mating edges of foil sheets 70 and 72. Bothheater assemblies 60 and 62 are foamed in place between the tray and theurethane foam.

Also foamed in place is a tray fill tube 76 of polypropylene in heattransfer relation to heater 62 to prevent freeze-up and adapted tosuppply water to fill tray 52 through the bottom wall 56 of the tray.Electrical leads may enter the freezer through tubing 77.

WATER FILL SYSTEM The water fill system 42 will now be described withreference to FIGS. 1 and 14. In general, water is supplied to tray 52from a reservoir 78 defined by a water valve housing 80 attached to theback wall 82 of the refrigerator behind the freezer compartment 26.Water in reservoir 78 communicates with tray 52 through outlet 84 in thereservoir housing and tubing or conduit means 86 connecting outlet 84with tray fill tube 76 through a protector tube base 90 (FIG. 4). Watercontained in tray 52 seeks a common level with water in reservoir 78.Thus, the desired fill level in the tray is achieved by predeterminingthe water level in reservoir 78.

To control the level of water in reservoir 78, water valve housing 80includes a float 94 pivotally attached at 96 to a wing hinge bracket 98.Top wall 100 of housing 80 carries a water valve assembly 102 includinga water inlet 104 and a water outlet 106. A domestic supply of purifiedwater may be connected to the inlet 104. Valve pin 108 (slidablysupported on three ribs 109) has a rubber valve portion 110 adapted forclosing against a valve seat 112. At the lower end of assembly 102, avalve pin actuator 114 pivots about axis 116 in response to the upwardforce of float 94 at one end 120 as balanced against a water leveladjustment mechanism 122 at the other end 124. Water level may beadjusted by a remote knob 125 turning worm gears 126, 128 against spring130.

The water level is adjusted at 125 in a manner to shut off the watersupply at 110, 112 when the water level A (FIGS. 2 and 14) exists inboth reservoir 78 and tray 52. In general, a fresh charge of water issupplied to tray 52 during an ice harvesting cycle when grid 36 is outof the tray. It should be noted that water level A will be raised towater level B when the grid is in the tray. The grid is constructed in amanner to displace substantially all water from the tray into the gridcavities for making clear ice. In this way, the water so displaced isavailable to form cubes in the grid cavities and, accordingly, does notform an adhesive film of ice between the grid and tray which resists theseparation of grid and tray at the start of an ice harvesting cycle.

ICE CUBE GRID Ice cube grid 36 (FIGS. 2, 3 and 8) has characteristics ofpoor heat conduction and good flexibility at low temperature with goodice release and return memory. It is comprised ofa polypropylene housingdefining cavities 142 for a plurality of ice cubes. Each cavity 142 hasan inverted truncated pyramidal shape. On the outside of the housingbetween the cavity forming portions thereof, a flexible filler 146 ofRTV silicone rubber fills the space between the cube forming cavities onthe outside of grid 36. The filler material should have an anti-stickcharacteristic to aid in the release of the grid from the tray duringice harvesting. It should be sufficiently flexible to distribute forcesthroughout the grid when the grid is warped for harvesting cubes. Asidefrom these characteristics, the filler 146 serves to force water in thetray upwardly into the cube forming cavities of the grid. Thus, with thegrid in place in the tray (FIG. 2, solid line), water level A willbecome water level B.

ICE STORAGE BUCKET ASSEMBLY The ice storage bucket assembly 38 will bedescribed with reference to FIGS. 1 and 2. An ice container 150 of highimpact polystyrene rests on a steel wire shelf 152. The shelf pivotsabout a support foot 154 on the bottom wall 156 of freezer portion 26and includes an upright bracket 158 at the rear thereof which hangs froma weight sensing means 39 in a manner to keep the back 160 of the shelfspaced from the freezer wall 156. The ice container or bucket 150 isbuilt up with a high wall to catch the cubes falling from the grid 36above. In general, the weight sensing means 39 will in one mode reflectthe presence of ice container 150 on shelf 152 and, in another mode, thepresence of a full load of ice cubes within the container 150.

WEIGHT SENSING MEANS The weight sensing means 39 (FIGS. 1, 9 and I5) iscomprised ofa nylon weight shaft 176 having a hooked portion 178 forgripping a loop in the upright shelf bracket 158. The weigh shaft isconnected to a stainless steel container weigh bar 188 which pivotsabout 198 and is electrically connected to terminal 190 by restingthereon. An ice weigh bar 192, also stainless steel, is disposed abovethe container weigh bar and pivots about a brass pin 194. The other endof ice weigh bar 192 normally rests in electrically conductingrelationship against a brass weigh bar stop and terminal 196. Thecontainer weigh bar includes a terminal 198 which cooperates withterminal 196 to comprise a weigh switch. In brief, the presence ofcontainer 150 on shelf 152 will cause the weigh shaft 176 to pull downin a manner to cause container weigh bar 188 to touch ice weigh bar 192and complete a circuit between terminals 198 and 196. When container 150fills up with a predetermined full load of ice cubes, the furtherdownward movement of weigh shaft 176 will cause container weigh bar 188to force ice weigh bar 192 out of electrical contact with terminal 196thereby breaking the circuit.

HARVESTING MECHANISM The harvesting mechanism 40 will now be describedwith reference to FIGS. 9, 10, ll, 12, 13 and 15. With particularreference to FIGS. 12 and 13, the harvesting mechanism is comprised of abox-like plastic casing 210 defining a compartment 212 for the gridpivoting and twisting gears on one side of a gear mounting plate 214. Onthe other side of the mounting plate 214, the housing is divided into adrive compartment 216 and a cam compartment 218.

The means for pivoting or removing and twisting or warping grid 36 aredisposed in gear compartment 212. A cam and crank gear 220 is rotatablymounted on plate 214 and is rotatably driven from the other side of theplate by a pair of worm gears 222, 224 which are, in turn, driven bydrive motor assembly 226. The cam and crank gear 220 is comprised of acam portion 230 and a gear portion 232. The cam 230 cooperates with atimer holding switch 234 through a switch actuator 236 so that the timerholding switch is closed when the switch actuator 236 rides the outerperiphery of the cam. Timer holding switch 234 is in shunt with weightswitch 196, 198. In the position of FIG. 12, switch actuator 236 isdisposed in a notched portion of the cam periphery to open switch 234.Gear 232 directly drives a cam gear 240 and includes a crank portion 242in a slot 244 of segment gear 246. Thus, one rotation of crank and camgear 220 will cause the segment gear 246 to rock back and forth aboutits pivot point 250.

The segment gear is drivably connected to grid drive gear 252 whichextends outside the mechanism casing 210 where a D socket 254 is adaptedfor connection with a similarly shaped stud on grid 36 as at 256 (FIG.3).

Cam gear 240 is pivotally mounted on mounting plate 214 and extendstherethrough for directly driving cam 260 and cam 274. Cam 260 operatesa second timer holding switch 262 through a switch actuator 264 so thatthe timer holding switch is closed when the switch actuator rides theouter periphery of the cam. Thus, switch 262 is shown in its openposition.

In accordance with this invention, an ice making cycle is timed andcontrolled through a defrost timer 268 which otherwise has theconventional function of periodically defrosting the refrigerator.

OPERATION An ice making cycle in accordance with the teachings of thisinvention will now be described. Water level in reservoir 78 is adjustedby means of water level adjustment 125 to provide a predetermined waterlevel A when grid 36 is not in tray 52. Once the adjustment is made,water valve 110, 112 will be opened and closed by the action of float 94and lever 114 to rapidly return to this water level during the time thatgrid 36 is being' rotated out of tray 52 during an ice harvesting cycle.

With grid 36 in tray 52, substantially all of the water comprising waterlevel A will be forced through the open bottom of each grid cavity 142to form a water level B near the top of the grid cavities. This waterlevel B will provide in the embodiment shown a water depth ofapproximately one inch in the tray. Fan means 285 (FIG. 15) blows airthrough and includes a duct 290 on the back wall of the freezercompartment 26 which distributes a quantity (10 to 15 cubic feet perminute) of below-freezing air (minus 10 F. to minus l2 F.) uniformlyover the exposed top planar surface (water level B) of the water in thegrid cavities. The air is cooled by refrigerating or cooling meansincluding a compressor 286 and a temperature responsive cold control 289for controlling fan means 285 and compressor 286. The refrigeratingmeans may include a defrost arrangement including a defrost heater 287and limiter switch 288 in series with a defrost timer contact 4.Additional distribution may be accomplished by suitable means such asadjustable louvers 292 at the duct 290.

A skim of clear ice (FIG. 3) starts to form at water level B along thetop planar surface of water filling each cube cavity 142. Ice thickensfrom this top surface progressively downwardly. During the generation ofthis ice, heater 60 is energized to heat the body of water in each cubecavity below the ice forming along the top surface of the body of waterin each cube cavity. Periodically (see FIGS. 15 and 16), defrost timer268 initiates a harvest cycle. This occurs when the clear ice is in theform of a cube 296 approximately one-half inch thick. With the ice makerin a 0 F. freezer and the refrigerator in a F. room ambient, compressor286 in the freezing system normally operates 60 70 percent of the time.These parameters provide for freezing clear ice Va inch thick in about2% hours. Thus, defrost timer 268 is designed to initiate three harvestcycles in the 8 hour program of the defrost timer.

Generally, by adding cam 260 to the harvest mechanism and ice makerswitch 261 and contact 5 to the defrost timer 268, the clear cube icemaker can be timed and controlled with the defrost timer. The harvestcan also be timed and oriented with respect to the defrost cycle. Theice maker contact 5 (FIGS. 15 and 16) must be closed long enough for theice harvest mechanism 40 to close cam operated timer switches 234 and262 but must open before the mechanism has completed its harvest cycle(10 minutes). FIG. 16 shows a suitable 8-hour cycle chart for defrosttimer 268. A defrost cycle is initiated once every 8 hours when contact4 is closed to energize defrost heater 287. The defrost cycle terminateswhen temperature responsive limiter switch 288 opens. As aforesaid,three harvest cycles are initiated during an 8 hour period, i.e., whencontact 5 is closed for 4 minutes at the beginning of the period, after3 hours and again after 5 /2 hours. As can be seen in FIGS. 15 and 16,the defrost timer motor 269 runs continuously (contact 1 energized) andthe compressor 286 and fan 285 are deenergized during defrost (contact 2open when contact 4 closed).

More particularly, the ice maker switch 261 and contact 5 in the defrosttimer energize a relay coil 270 which closes a bistable timer switch 272in the harvest mechanism. Bistable means that timer switch 272 has thecharacteristic of stability in both its open and closed positions. Thus,bistable timer switch 272 remains closed (even after the relay coil isdeenergized when switch 261 in the defrost timer opens after 4 minutes)until the harvest mechanism is operated through its harvest cycle bydrive motor 226. Half way through the harvest cycle, a cam 274 in theharvest mechanism pushes switch 272 open. Cam operated timer switches234 and 262 are closed at the time switch 272 is pushed open to allowthe mechanism to complete the harvest cycle by maintaining theenergization of driver motor 226. Timer switch 272 remains open untilthe defrost timer ice maker switch 261 closes again for 4 minutes at itsnext following point (after I minutes) in the timer cycle chart. Thebistable relay switching arrangement prevents the ice maker from missinga harvest cycle when the defrost timer switch 261 closes at the sametime the weigh switch contact 196 is open due to the bucket being fullor removed from the freezer. Moreover, as long as timer switch 272 inthe mechanism is closed, the extra tray bottom heater 62 will beenergized thus preventing the water in the tray from freezing to thebottom if the harvest cycle is to be delayed. This is the primarypurpose for the bistable relay switching arrangement when using thedefrost timer to time the clear cube ice maker.

With reference to FIGS. 2 and 3, grid 36 starts to rotate withsubstantially /2 inch cubes 296 of clear ice in the top portion only ofeach cavity 142. Unfrozen water 298 beneath the cubes remains in tray 52in a liquid state. Tray housing 50 includes an upstanding flange 300journalling a stud 302 projecting from one corner of the grid. A stud atthe same corner on the opposite end of the grid (not shown) fits in theD socket 254 of grid drive gear 252. As grid 36 rotates from theinstalled position X (FIG. 2) through the upright position Y to theharvesting position Z, the grid will engage a raised boss 304 whichhalts the pivoting motion of the grid at its outer end. However, theharvesting mechanism continues to drive the grid causing the end nearestthe driving mechanism to continue rotation to warp the grid in a mannerto release clear ice cubes 296 from the grid. The released cubes fallinto the ice bucket 38 therebelow.

After the cubes are harvested, the continued rotation of crank gear 232operating through its crank 242 in the slot of segment gear 246 willreturn the grid to its installed position X.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is: g

l. A clear ice maker for a freezer having defrost means and a defrosttimer for periodically defrosting said freezer, said ice makercomprising a tray having walls adapted to contain a body of water, agrid in said tray having cavity-forming means for displacing the body ofwater contained by said walls into the cavity, means distributingsubfreezing air over the top planar surface of said body of water insaid grid cavity for a sufficient period to initiate the freezing ofclear ice in said grid cavity along the interface between said air andsaid top planar surface and to continue the freezing of clear icedownwardly in said grid cavity, and a bucket for storing said clear icein said freezer and being removable from said freezer, tray heatingmeans energizable to maintain said body of water in a liquid stateadjacent said tray below the freezing clear ice, and barvestingmechanism operable in a harvest cycle by a drive motor for removing saidgrid and clear ice from said tray before the freezing of clear icedownwardly in said grid cavity reaches the bottom wall of said tray andfor depositing said clear ice in said bucket, said harvesting mechanismincluding a weigh switch, a bistable first timer switch and said drivemotor in series electrical flow relationship, said first timer switchhaving the characteristic of stability in both its open and closedpositions and operating in its closed position to enable the initiationof said harvest cycle by operating said harvest mechanism when saidweigh switch is closed, said weigh switch having a closed position whensaid bucket is empty and an open position when said bucket is full ofclear ice or removed from said freezer, said harvesting mechanism havinga second timer switch in shunt with said weigh switch and a third timerswitch in shunt with said first timer switch, said drive motor operatingto actuate said second and third timer switches to maintain theoperation of said drive motor and harvesting mechanism once said harvestcycle is initiated irrespective of said weigh switch and said firsttimer switch, said drive motor operating to actuate said second andthird timer switches to terminate said harvest cycle, and said drivemotor operating to move said first timer switch to its stable openposition after said second and third timer swiches have been actuated tomaintain the operation of said drive motor and before said harvest cycleis terminated, said heating means comprising a heater for a wall of thetray in shunt with said weigh switch and said second timer switch and inseries electrical flow relationship with said first timer switch, saiddefrost timer including ice maker means initially operable to move saidfirst timer switch to its stable closed position when said freezer isnot being defrosted and subsequently operable to permit the movement ofsaid first timer switch to its stable open position whereby said heateris adapted for temporary energization when a harvest cycle is initiatedby the movement of said first timer switch to its stable closed positionand said bucket is either full of clear ice or removed from saidfreezer, said temporary energization continuing until said bucket isreplaced in said freezer and is no longer full.

2. In a clear ice maker for a freezer having defrost means anda defrosttimer including means for periodically defrosting said freezer byenergizing said defrost means, said ice maker including a tray havingside and bottom walls adapted to contain a body of water, a grid in saidtray having cavity-forming means for displacing the body of watercontained by said walls into the cavity, fan means distributingsubfreezing air over the top planar surface of said body of water insaid grid cavity for a sufficient period to initiate the freezing ofclear ice in said grid cavity along the interface between said air andsaid top planar surface and to continue the freezing of clear icedownwardly in said'grid cavity, a bucket for storing said clear ice insaid freezer and being removable from said freezer, and tray heatingmeans energizable to maintain said body of water in a liquid stateadjacent said tray below the freezing clear ice, the improvementcomprising harvesting mechanism operable in a harvest cycle by a drivemotor for removing said grid and clear ice from said tray before thefreezing of clear ice downwardly in said grid cavity reaches the bottomwall of said tray and for depositing said clear ice in said bucket, saidharvesting mechanism including a weigh switch, a bistable first timerswitch and said drive motor in series electrical flow relationship, saidfirst timer switch having the characteristic of stability in both itsopen and closed positions and operating in its closed position to enablethe initiation of said harvest cycle by operating said harvest mechanismwhen said weigh switch is closed, said weigh switch having a closedposition when said bucket is empty and an open position when said bucketis full of clear ice or removed from said freezer, said harvestingmechanism having a second timer switch in shunt with said weigh switchand a third timer switch in shunt with said first timer switch, saidsecond and third timer switches and said drive motor being in serieselectrical flow relationship, said drive motor operating to close saidsecond and third timer switches to maintain the operation of theharvesting mechanism once said harvest cycle is initiated irrespectiveof said weigh switch and said first timer switch, said drive motoroperating to open said second and third timer switches to terminate saidharvest cycle, and said drive motor operating to move said first timerswitch to its stable open position after said second and third timerswitches are closed and before said harvest cycle is terminated, saidheating means comprising a heater for said tray in shunt with said weighswitch and said second timer switch and in series electrical flowrelationship with said first and third timer switches, said defrosttimer including ice maker means initially operable to move said firsttimer switch to its stable closed position when said freezer is notbeing defrosted and subsequently operable to facilitate the movement ofsaid first timer switch to its stable open position whereby said heateris adapted for temporary energization when a harvest cycle is initiatedby the movement of said first timer switch to its stable closed positionand said bucket is either full of clear ice or removed from saidfreezer, said temporary energization continuing until said bucket isreplaced in said freezer and is no longer full.

3. The improved harvesting mechanism of claim 2 wherein said ice makermeans comprises a timer switch in said defrost timer and a relay coilfor moving said first timer switch to its stable closed position.

4. The improved harvesting mechanism of claim 2 wherein said harvestcycle is substantially 10 minutes and said defrost timer is adapted tooperate said ice maker means to initiate said harvest cyclesubstantially three times in an 8 hour period.

5. A clear ice maker for a freezer having defrost means and a defrosttimer including means for periodically defrosting said freezer byenergizing said defrost means, said ice maker comprising a tray havingside and bottom walls adapted to contain a body of water, a grid in saidtray having cavity-forming means for displacing the body of watercontained by said walls into the cavity, fan means distributingsubfreezing air over the top planar surface of said body of water insaid grid cavity for a sufficient period to initiate the freezing ofclear ice in said grid cavity along the interface between said air andsaid top planar surface and to continue the freezing of clear icedownwardly in said grid cavity, and a bucket for storing said clear icein said freezer and being removable from said freezer, tray heatingmeans energizable to maintain said body of water in a liquid stateadjacent said tray below the freezing clear ice, and harvestingmechanism operable in a harvest cycle by a drive motor for removing saidgrid and clear ice from said tray before the freezing of clear icedownwardly in said grid cavity reaches the bottom wall of said tray andfor depositing said clear ice in said bucket, said harvesting mechanismincluding a weigh switch, a bistable first timer switch and said drivemotor in series electrical flow relationship, said first timer switchhaving the characteristic of stability in both its open and closedpositions and operating in its closed position to enable the initiationof said harvest cycle by operating said harvest mechanism when saidweigh switch is closed, said weigh switch having a closed position whensaid bucket is empty and an open position when said bucket is full ofclear ice or removed from said freezer, said harvesting mechanism havinga second timer switch in shunt with said weigh switch and a third timerswitch in shunt with said first timer switch, said second and thirdtimer switches and said drive motor being in series electrical flowrelationship, said drive motor operating to close said second and thirdtimer switches to maintain the operation of the harvesting mechanismonce said harvest cycle is initiated irrespective of said weigh switchand said first timer switch, said drive motor operating to open saidsecond and third timer switches to terminate said harvest cycle, andsaid drive motor operating to move said first timer switch to its stableopen position after said second and third timer switches are closed andbefore said harvest cycle is terminated, said heating means comprising afirst heater for the sidewall of the tray in'shunt with said weighswitch and said first, second and third timer switches and a secondheater for the bottom wall of the tray in shunt with said weigh switchand said second timer switch and in series electrical flow relationshipwith said first and third timer switches, said defrost timer includingice maker switch means closable to move said first timer switch to itsstable closed position when said freezer is not being defrosted andopenable before said first timer switch is moved to its stable openposition whereby said first heater is adapted for continuousenergization and said second heater is adapted for temporaryenergization when a harvest cycle is initiated and said bucket is eitherfull of clear ice or removed from said freezer, said temporaryenergization continuing until said bucket is replaced in said freezerand is no longer full and the delayed harvest cycle thus initiated issubsequently terminated.

1. A clear ice maker for a freezer having defrost means and a defrosttimer for periodically defrosting said freezer, said ice makercomprising a tray having walls adapted to contain a body of water, agrid in said tray having cavity-forming means for displacing the body ofwater contained by said walls into the cavity, means distributingsubfreezing air over the top planar surface of said body of water insaid grid cavity for a sufficient period to initiate the freezing ofclear Ice in said grid cavity along the interface between said air andsaid top planar surface and to continue the freezing of clear icedownwardly in said grid cavity, and a bucket for storing said clear icein said freezer and being removable from said freezer, tray heatingmeans energizable to maintain said body of water in a liquid stateadjacent said tray below the freezing clear ice, and harvestingmechanism operable in a harvest cycle by a drive motor for removing saidgrid and clear ice from said tray before the freezing of clear icedownwardly in said grid cavity reaches the bottom wall of said tray andfor depositing said clear ice in said bucket, said harvesting mechanismincluding a weigh switch, a bistable first timer switch and said drivemotor in series electrical flow relationship, said first timer switchhaving the characteristic of stability in both its open and closedpositions and operating in its closed position to enable the initiationof said harvest cycle by operating said harvest mechanism when saidweigh switch is closed, said weigh switch having a closed position whensaid bucket is empty and an open position when said bucket is full ofclear ice or removed from said freezer, said harvesting mechanism havinga second timer switch in shunt with said weigh switch and a third timerswitch in shunt with said first timer switch, said drive motor operatingto actuate said second and third timer switches to maintain theoperation of said drive motor and harvesting mechanism once said harvestcycle is initiated irrespective of said weigh switch and said firsttimer switch, said drive motor operating to actuate said second andthird timer switches to terminate said harvest cycle, and said drivemotor operating to move said first timer switch to its stable openposition after said second and third timer swiches have been actuated tomaintain the operation of said drive motor and before said harvest cycleis terminated, said heating means comprising a heater for a wall of thetray in shunt with said weigh switch and said second timer switch and inseries electrical flow relationship with said first timer switch, saiddefrost timer including ice maker means initially operable to move saidfirst timer switch to its stable closed position when said freezer isnot being defrosted and subsequently operable to permit the movement ofsaid first timer switch to its stable open position whereby said heateris adapted for temporary energization when a harvest cycle is initiatedby the movement of said first timer switch to its stable closed positionand said bucket is either full of clear ice or removed from saidfreezer, said temporary energization continuing until said bucket isreplaced in said freezer and is no longer full.
 2. In a clear ice makerfor a freezer having defrost means and a defrost timer including meansfor periodically defrosting said freezer by energizing said defrostmeans, said ice maker including a tray having side and bottom wallsadapted to contain a body of water, a grid in said tray havingcavity-forming means for displacing the body of water contained by saidwalls into the cavity, fan means distributing subfreezing air over thetop planar surface of said body of water in said grid cavity for asufficient period to initiate the freezing of clear ice in said gridcavity along the interface between said air and said top planar surfaceand to continue the freezing of clear ice downwardly in said gridcavity, a bucket for storing said clear ice in said freezer and beingremovable from said freezer, and tray heating means energizable tomaintain said body of water in a liquid state adjacent said tray belowthe freezing clear ice, the improvement comprising harvesting mechanismoperable in a harvest cycle by a drive motor for removing said grid andclear ice from said tray before the freezing of clear ice downwardly insaid grid cavity reaches the bottom wall of said tray and for depositingsaid clear ice in said bucket, said harvesting mechanism including Aweigh switch, a bistable first timer switch and said drive motor inseries electrical flow relationship, said first timer switch having thecharacteristic of stability in both its open and closed positions andoperating in its closed position to enable the initiation of saidharvest cycle by operating said harvest mechanism when said weigh switchis closed, said weigh switch having a closed position when said bucketis empty and an open position when said bucket is full of clear ice orremoved from said freezer, said harvesting mechanism having a secondtimer switch in shunt with said weigh switch and a third timer switch inshunt with said first timer switch, said second and third timer switchesand said drive motor being in series electrical flow relationship, saiddrive motor operating to close said second and third timer switches tomaintain the operation of the harvesting mechanism once said harvestcycle is initiated irrespective of said weigh switch and said firsttimer switch, said drive motor operating to open said second and thirdtimer switches to terminate said harvest cycle, and said drive motoroperating to move said first timer switch to its stable open positionafter said second and third timer switches are closed and before saidharvest cycle is terminated, said heating means comprising a heater forsaid tray in shunt with said weigh switch and said second timer switchand in series electrical flow relationship with said first and thirdtimer switches, said defrost timer including ice maker means initiallyoperable to move said first timer switch to its stable closed positionwhen said freezer is not being defrosted and subsequently operable tofacilitate the movement of said first timer switch to its stable openposition whereby said heater is adapted for temporary energization whena harvest cycle is initiated by the movement of said first timer switchto its stable closed position and said bucket is either full of clearice or removed from said freezer, said temporary energization continuinguntil said bucket is replaced in said freezer and is no longer full. 3.The improved harvesting mechanism of claim 2 wherein said ice makermeans comprises a timer switch in said defrost timer and a relay coilfor moving said first timer switch to its stable closed position.
 4. Theimproved harvesting mechanism of claim 2 wherein said harvest cycle issubstantially 10 minutes and said defrost timer is adapted to operatesaid ice maker means to initiate said harvest cycle substantially threetimes in an 8 hour period.
 5. A clear ice maker for a freezer havingdefrost means and a defrost timer including means for periodicallydefrosting said freezer by energizing said defrost means, said ice makercomprising a tray having side and bottom walls adapted to contain a bodyof water, a grid in said tray having cavity-forming means for displacingthe body of water contained by said walls into the cavity, fan meansdistributing subfreezing air over the top planar surface of said body ofwater in said grid cavity for a sufficient period to initiate thefreezing of clear ice in said grid cavity along the interface betweensaid air and said top planar surface and to continue the freezing ofclear ice downwardly in said grid cavity, and a bucket for storing saidclear ice in said freezer and being removable from said freezer, trayheating means energizable to maintain said body of water in a liquidstate adjacent said tray below the freezing clear ice, and harvestingmechanism operable in a harvest cycle by a drive motor for removing saidgrid and clear ice from said tray before the freezing of clear icedownwardly in said grid cavity reaches the bottom wall of said tray andfor depositing said clear ice in said bucket, said harvesting mechanismincluding a weigh switch, a bistable first timer switch and said drivemotor in series electrical flow relationship, said first timer switchhaving the characteristic of stability in both its open and closedpositionS and operating in its closed position to enable the initiationof said harvest cycle by operating said harvest mechanism when saidweigh switch is closed, said weigh switch having a closed position whensaid bucket is empty and an open position when said bucket is full ofclear ice or removed from said freezer, said harvesting mechanism havinga second timer switch in shunt with said weigh switch and a third timerswitch in shunt with said first timer switch, said second and thirdtimer switches and said drive motor being in series electrical flowrelationship, said drive motor operating to close said second and thirdtimer switches to maintain the operation of the harvesting mechanismonce said harvest cycle is initiated irrespective of said weigh switchand said first timer switch, said drive motor operating to open saidsecond and third timer switches to terminate said harvest cycle, andsaid drive motor operating to move said first timer switch to its stableopen position after said second and third timer switches are closed andbefore said harvest cycle is terminated, said heating means comprising afirst heater for the sidewall of the tray in shunt with said weighswitch and said first, second and third timer switches and a secondheater for the bottom wall of the tray in shunt with said weigh switchand said second timer switch and in series electrical flow relationshipwith said first and third timer switches, said defrost timer includingice maker switch means closable to move said first timer switch to itsstable closed position when said freezer is not being defrosted andopenable before said first timer switch is moved to its stable openposition whereby said first heater is adapted for continuousenergization and said second heater is adapted for temporaryenergization when a harvest cycle is initiated and said bucket is eitherfull of clear ice or removed from said freezer, said temporaryenergization continuing until said bucket is replaced in said freezerand is no longer full and the delayed harvest cycle thus initiated issubsequently terminated.